Apparatus for transmitting seismic signals



Feb. 6, 1945. E. M. sHooK E-rAl.

APPARATUS FOR TRANSMITTING SEISMIC SIGNLS- Original Filed March 2o, 1940 8 Sheets-Sheet l E. M. SHOCK ETAL 2,369,081

APPARATUS FOR TRANSMITTING SEISMIC SIGNALS original Filed March 2o, 1940 a sheetssheet 2v 6'41 144A/UME 7 En? ro comm/wanna l//v/r ranno/vs LINE GEOPHO/VF Feb. 6, 1945.

E. M. SHOOK El' AL APPARATUS FOR TRANSMITTING SEISMIC SIGNALS Original Filed March 20, 1940 8 Sheets-Sheet 3 El 4J HK Fb- 5 1945- E.. M. SHOOK ETAL 2,369,081

APPARATUS FOR TRANSMITTING SEISMIC SIGNALS Original Filed March 20, 1940 8 Sheets-Sheet 4 HUMALA vvvvvvvvvv Febo 6, 1945. E. M. sHooK Erm..

APPARATUS FOR TRANSMITTING SEISMIC SIGNALS 8 Sheets-Sheet 5 Original Filed March 20, 1940 atta/mug A vvvvvvvvvvvvv KN INI AFSF 3945 E. M. SHOCK TAL 2,369,081l

APPARATUS FOR TRANSMITTING SEISMIC 'SIGNALS Original Filed March 20, 1940 8 Sheets-Sheet 6 AA LA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA vvvvvvvvvvvvvv'vvvv'VVVvvvvvvvvvvVYYVVVVVVYVWYYVVVY www 8 sheets-sheet 7 Feb. 6, R945. E. M. sHooK ETAL APPARATUS FOR TRANSMITTING SEISMIC SIGNALS Original Filed March 20, 1940 Feb. 6, E945, E. M. sHooK Erm.

APPARATUS FOR TRANSMITTING SEISMIC SIGNALS Original Filed March 20, 1940 8 Sheets-Sheet 8 Patenied Feb. 6, i945 iran STATES APPARATUS Fon 'rnANsMrrriNG saisine i sIGNALs lEarley M. Shook and Robert W. Olson, Washington, D. C., assignors, by mesne assignments, to Soc'ony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York Original application March 20,- 1940, Serial No.

324,930, now Patent No. 2,340,275, dated .anuary 25, 1944. Divided and this application March l2, 1943, Serial No. 478,943

9 Claims.v (Cl. 177-352) IThis application is a division of our copending application Serial No. 324,930, filed March 20, 1940, which on January 25, 1944, issued as `Patent No. 2,340,275.

This invention relates to apparatus for recording seismic waves and more particularly to apparatus for recording the instant of detonation of a charge of explosives which creates seismic Waves in the earths surface and means for automatically disconnecting a detector or geophone that is used to detect vertically traveling Waves from the explosive charge which creates the seismic waves in the earths surface. Additionally, this inventionv contemplates means for producing the above enumerated results Without disrupting the process of recording seismic waves in the manner which has been practiced heretofore in the art of reilection seismic survey.

In the art of seismic prospecting, it has heretofore, been necessaryto provide means which will respond to an electrical impulse for producing an indication of the instant of 'detonation ci an explosive charge. This indication when recorded on a seismogram is known in the art as the time break. To produce such a time break with some forms of apparatus known it is necessary that reliance must be placed upon an operator for properly connecting the circuits which detonate the charge of explosive. With this particular type of apparatus if the detonator for the explosive charge has been improperly connected, the rupture of the detonating circuit will produce a transient voltage that is of a polarity that willnot be transmitted 'through the apparatus to the recorder. This would result in an erroneous time break that would come from subsequent impulses which have been generated by making and breaking the detonating circuit after the charge of explosives has been detonated. By the instant invention it is possible to eliminate these dimculties by providing suitable circuits whereby, regardless of the polarity of the' transient voltage generated in the detonating circuit, the rupturing of the detonating circuit will produce an indication on the seismogram that is being recorded which will be accurate and a true indication of the instant of detonation of the explosive charge.

In addition to the time break circuit described above, a zzimber of other circuits by means of which the instant of detcnation can be registered on a seismograph are known. Some of these do not discriminate as to the polarity of the electrical 'impulse which indicates the instant of detonation. Although these circuits do vnot have polarity discrimination they have not proven entirely satisfactory due to the fact that no means have been provided for eliminating spurious voltages which when recorded on a seismograph would appear as time breaks. These objectionable features have been overcome by the instant invention.

When conducting a seismic survey of a particular area it is always necessary that consideration be taken .of the weathered unconsolidated strata of the. earths surface for in this strata the velocity of Wave travel is considerably less than the velocity of waveA travel in the denser media. If one fails to take cognizance of this fact, errors are introduced in both the correlation and the subsequent profiles computed from the data for this particular area. Therefore, thisv invention further contemplates apparatus for recording data from which thewords, means are provided whereby there can be recorded on a single trace of a multiple-trace. seismogram the time break, the rst break or breaks arriving at the uphole geophone, the rst break of a geophone in the conventional spread and subsequent waves comprising retracted and reiiected waves which are detected by this geophone. A conventional spread such as that referred to in this application is of the typeused in reflection or refraction seismic surveying, that is, the geophones are collaterally spaced from the shot point.

From the above it is obvious that the ldifficulties encountered by those practicing the methods of the prior art are obviated in that all the data that is necessary from a single spread when shot in one direction can be recorded on a single seismogram. This record will include a time break indicative of the instant of detcnation of the explosive charge which creates 'the seismic waves in the earths surface, the time consumed by the vertically traveling waves from the explosive charge to the surface and the time required for these waves which have been created by the explosive charge to travel downwardly to the interfaces of the subsurface strata and be reflected back to the geophones which have vbeen collaterally spaced from the shot point.

Reverting to the phase of the instant inveninvolved is completely eliminated in that regardless of the manner in which the detonating circuit is made up, the transient voltage resulting from the current dying out of the deton- -ting circuit will always initiate the operation of means which will mark the exact instant of the detonation of the explosive charge The foregoing features form the principal subjects matter of the claims in the present application.

Another feature of the instant invention resides in the provision of novel means whereby the indication of the instant of detonation, the time break impulse, as well as the rst impulse from the uphole geophone can be communicated from the shot point to the recording apparatus by means of telephone or radio. The local terrain of a particular area in many instances makes the use of telephone lines or conductors very impractical, particularly when the survey is being conducted on bodies of water, such as lakes, or in swamps. This feature, including means for rendering the voice transmitting means ineffective after transmission of either or both the time break and uphole geophone Y impulse, forms the subject matter of applicants divisional application, Serial Number 478,944, filed March 12, 1943, and entitled Apparatus for recording seismic waves."

Therefore, a primary object of this invention resides in the provision of' apparatus for accurately producing on a seismogram an indication Still another object ot this invention resides in the provision of means whereby a plurality of data can be recorded on a single trace of a seismogram in such a manner that any -one datum will not interfere with the other data.

Other` objects and advantages of this invention will be apparent from the following de" tailed description when considered in connection with the drawings in which: Y

Figure 1 is a diagrammatic illustration of a circuit by means of which the time break impulse regardless of polarity can be transmitted to the recording unit by means of telephonie communication;

Figure 2 is a diagrammatic illustration of an electrical circuit which differs from that shown in Figure 1 in that the system is connected by capacitances to the telephonie communication system;

Figure 3 is a diagrammatic illustration of a circuit by means of which the time break can be communicated to the recording unit showing the push-push time break circuit located at the recording' end of the telephone line;

Figure 4 is a modification of the circuit shown in Figure 3; v

Figure 5 is still another modification of this circuit;

Figure 6 is a composite wiring diagram of electrical circuits by means of which voice communication can bevhad between' the shot flrer and 'the recording instrument operator, means for of the exact instant of detonation of an explosive n charge that is used to create seismic waves in N the earths surface.

Another object of this invention resides in the provision \of a method for recording on a single trace the time break, the waves which correspond to vertically traveling seismic waves, from the explosive charge to the surface, and the waves which correspond to the seismic waves which have traveled downwardly to the interfaces of the substrata and have been reflected, to the surface. The method aspects form the subjects matter of the above parent application, Serial Number 324,930, now Patent No. 2,340,275.

This invention also contemplates means for 'cuit after detonation occurs and iirst breaks such automatically disconnecting or rendering inoperative the uphole geophone after the waves which travel vertically from the explosive charge have been detected. l

y It is still a further object of this invention to provide means for automatically rendering inoperative the uphole geophone after the vertiy cally traveling waves havebeen detected and prior to the reception of waves which have aveled directly to the spread geophones, and ose which have been reflected from the interfaces of subsurface strata.

Still another object of this invention resides in the provision of means for communicating communicating the time break impulse to the recorder and means for communicating the first impulse from the uphole geophone to the recorder; v

Figure 7 is a modification of the circuit diagram show n in Figure l differing therefrom in that the time break impulse is communicated to the recorder by means of radio;

Figure 8 differs from Figure 7 in that circuits are provided whereby the first impulses received by the uphole geophone are also communicated to the recorder by means of radio;

Figure 9 is a modification of the invention illustrated in Figure 8. By means of the circuits illustrated in this diagramthe same data can be communicated by radio to the recorder;

Figure 10 is a wiring diagram of an electrical circuit of another modification of this invention by means of'which the time break and the uphole geophone impulses can 'be communicated to the recording instrument;

as those received by any one of the geophones of the spread on one trace and the uphole geophone impulse on the other'trace;

Figure 12 illustrates atypical record-of the 'if type recorded when using the invention forming the subject matter of this appucation. The im- Ipulse corresponding to the uphole geophone signal has been recorded'on a separate trace;

Figure 13 is an illustration of a single trace of the time break and the first impulse from the using the invention forming the 'subject matter of this application showing the time break, the uphole geophone impulses and the iirst break on the same trace of the seismogram in such a manner that any one of the three Vwill not obscure the other; and

Figure 14 illustrates one trace of a seismogram aseaoer on which the time break, the uphole geophone impulses, the rst break, and subsequent reflections have been recorded.

Referring to the drawings in detail, in particular, Figure 1, there is shown a circuit diagram of one phase of this invention which deals with the communication of a signal, indicative of the instant of detonation of an explosive charge to create seismic waves in the earths surface, to a recorder. By means of this electrical circuit a signal indicative of the true instant of detonation will be transmitted to the recording apparatus regardless of the polarity of the signal voltage generated when the blaster circuit is ruptured by the detonation of the explosive. The current dying out of the,blaster circuit, illustrated by block diagram at lll, produces a transient voltage that will be communicated to the resistance l l by means of the conductors l2 and i3. Current ilowing through the resistance li will produce an instantaneous voltage drop across this resistance which serves as a charging potential for condensers ld and l5. Condensers l@ and l5 are in the grid circuit of the gas triode tubes I6 and il. ly known by the trade name thyratron. Their characteristics are such that when a negative potential of sufficient magnitude has been placed on their grids, by means of the battery lfno plate current will flow. When this negative bias has been removed or in part equalized, the grid will lose control in the tubes and plate current will fiow until it has been interrupted by some means. Therefore, a charging potential placed on condensers lli and l5, depending upon its polarity, will cause one of the tubes I6 or il to re, resulting in the iiow of plate current through resistance I9 or 26 to charge condenser 2l. The plate current in charging condenser 2l will produce a voltage drop across resistor 22. This voltage drop across the resistor 22 being in the form of a pulse can be impressed upon the primary winding 23 of a transformer 2d to produce a cor- These tubes are of the type commonresponding signal in the secondary windings 25 and 26. By means of conductors 2l and 28 this transformed voltage pulse is communicated to the communication unit 29 and through the communication unit by means of conductors 30 and Si to the recording galvanometer 32, where it is recorded on a trace of the seismogram.

Tubes i6 and Il are provided with a` common grid bias potential i8. By connecting these two 'tubes in the manner shown in Figure l, one of the tubes will re on the first impulse received from theblaster circuit regardless of its polarity. After one of the tubes has fired to produce a current in the plate circuit, the condenser 2| is charged, and once this condenser'has become charged, plate current can no longer iiow in the circuit. Therefore, the second tube will be pre-- vented from ring on subsequent impulses which are of opposite polarity to the first impulse received. 'Ihe condenser 2| therefore in eiect acts as a trap to stop the iiow of plate current from the gas triodes I6 and Il. Additionally, after one of the gas triodes I6 vor I1 has red, no further signals' will be communicated to the recorder from the blasting circuit. This condition will exist until condenser 2| has been discharged through the resistance 2|'. This will eliminate spurious voltages generated by the detonating circuit and blaster itself from being communicated to the l recorder and recorded. on the seismogram trace. In order to hold duplex communication with the operator at the recording apparatus, the secnot large enough to reduce voice currents appreciably.

lThe remainder of the electric seismograph is shown in block-diagram. The geophone may be a geophone of a conventional spread. This geophone is connected by means of conductors 36 to the input of an amplier 3l'. The output of the amplier 37 is connected by means of conductors 38 to the recording galvanometer 32.

In some cases it is desirable to use the time break impulse received from the blaster circuit to initiate the operation of a master control which controls the gain in amplification derived from one or more amplifiers. When this is the case, the communication unit 2S is connected to the master control Se by means of conductors Gil. The master control then is. appropriately connected to the amplier through leads di. Although for purposes of explanation a single geophone 35 is shown in thisgure, it is apparent to those skilled in the art that a plurality of geophones are used with their respective amplifierswhen doing refiection seismic survey work.

In Figure 2 there is shown a slight modification of the circuit illustrated in Figure l. rihe circuit of Figure 2 differs from that of Figure i in that the plate circuit of the gas triode tubes l 6 and il is capacitively connected by means of condensers t2, and i3 to the conductors 2l and 28 instead of by means of the transformer 2d shown in Figure l. The microphone 33 and receiver S13 in the circuit of Figure 2 are connected in series and across the leads 2l and 25 on the opposite side of condensers 152 and t3 from the resistance 22. This circuit functions in the same manner described in connection with Figure l.

Still another modification of this invention is l shown in Figure 3. in this instance the time break circuit is located not at the shot point but at the recording location. The impulse generated by the rupturing of the blasting circuit its cornmunicated by means of the telephone lines 2l and 28 to the resistance 543. This impulse regardless of its polarity produces an IR drop across this resistance which acts as a charging potential for the condensers t5 and 135. The current fiowing in the circuit while charging condensers db and 36 produces an IRl drop across the resistances di and 8. Depending upon the' polarity of the impulse received from the blaster, the IR drop across one of the resistors lil and lit? will add to'the grid bias as supplied by battery t9 on one of the gas triodes 5B or 5i to become sufficiently less negative that oneof the tubes will fire to produce a flow of plate current through its respective resistance 52 or 53 to charge the condenser 5a. The battery 55 is the usual plate potential supply. Current iiowing in' the plate circuit while -condenser 5t is becoming charged produces an IR drop across resistance 56 which can be recorded directly on a recording galvanometer 57 at the instant of rupturing of the detonating circuit. Duplex communication can behad between the shot rer and the recording instrument operator by means of the conventional communication equipment through the conductors 58, 59, 21, and

A further embodiment of this invention is illustrated by the circuit diagram in Figure 4. This circuit is intended to transmit a signal that is indicative of the instant of detonation of the explosive charge, the rst impulse received by the geophone that is placed adjacent the shot point, and speech by a single telephone channel and at the same time prevent the three pulsations from interfering with one another or from causing linterference on the record. The time break will be transmitted without polarity discrimination.

In this embodiment of the invention, the transient voltage produced in the detonating circuit of the blaster I0, in the manner described in connection with Figures 1, 2 and 3, causes one of the gas triodes I6 or I1 to fire. This is caused by the flow of current through resistors 41 and 48 which will produce an IR drop across them. The IR drop across one of these resistances will add to the bias potential supplied to one of the tubes I6 or I1 by means of the battery 60 in such a way as to cause the grid to lose control and the tube to become conductive. Current owing in the plate circuit will be in the form of a surge that will charge condenser 6 I. This impulse is transmitted through the battery 62, the resistance 63, back to the cathodes of the gas triodes I6 and I1. The iiow of this current through theI resistance 63 will cause the grid potential on the grid of gas triode tube 64 to become sufficiently less negative that the gas triode 64 will become conductive and a current will ow in its plate circuit. Inductance 65 is placed in the plate circuit so that there will be a delay in the build-up time for the plate current. The flow of current in the plate circuit of gas triode 64 produces an IR drop across the resistance 66 and resistance 61 which will cut oil the plate current from the amplifier tube or translating device 69. The period of time between the ring of gas triode 64 and cutting oil' the plate current from tube 69 is made suftlciently long that the uphole geophonewill have ample time to detect the rst impulse of waves traveling vertically upward from the explosive charge. This period of time is controlled by'inductance 65 plus resistances 66 and 61 and by varying the position of the tap 68 on the resistance 61. The plate current having been cut o from tube 69 after the impulse received from uphole geophone 10 has been ampliiied, transformed by the transformer 1| and communicated to the recording instrument by means of the conductors 12 and 13, no further signals can be communicated to the recording instrument l'and the same trace on which the time break and uphole geophone impulses were recorded can be used to record signals from one of the geophones in the conventional spread.' Additionally, since the tube 69 isolates the blaster, the time break/ and uphole geophone circuits from the telephone line and recording instrument, noises such as those produced by the microphone 14 which is .connected in the cathode circuit of tube 69 will n ot produce disturbances on the trace oi.' the seismogram. In

order to receive voice signals from the operatorofthe recording instrument over the telephone line formed by conductors 12 and 13, the secondary winding of. the transformer 1| is divided and a telephone receiver 15 is placed in series but between these twov windings. condenser 16 is connected across the telephone receiver.

The resistances 18 and 19 are placed in the plate circuits of the gas triodes I6 and l1 to com- The usual phone 'amplier tube I0 I namely, the transmission of the time break, the

first impulse from the uphole geophone, and telephone communication, can be transmitted over a single telephone channel. This circuit, like the one shown in Figure 4, will "transmit the time break Without polarity discrimination. The rst part of this circuit from the blaster through the two gas triodes I6 and I1 is identical with the circuit described and shown in Figure'4. The current from one of the gas triodes I6 or I1 will ow through the conductor 94, the milliammeter 95, the battery 96, the resistance 91, the conductor 98, back to the cathode of the gas triode I6 or I1. The ow of this plate current through the resistance 91 produces an 1R drop which will cause the bias potential supplied to the grid of gas triode 99 to become less negative to cause triode 99 to fire. The first impulse of'plate current flowing from gas triode 99 through condenser |00 will be impressed on the grid of an amplifier tube |0I. The amplified impulse will be transformed bythe transformer |02 and conducted by means of the telephone lines |03 and |04 to the recording galvanometer where it is recorded on one of the traces of a seismogram. Resistance |06 is a coupling resistance. The ow of plate current from gas triode 99 will also be through a portion of the resistance |06 to charge the condenser |01. The time required for condenser |01 to become fully charged is controlled by the position of the contactor on resistance |06. The fully charged p0- tential of condenser |01 serves as a grid bias for When this condenser reaches full charge, the bias placed on the amplifier tube |0I is sufficient to entirely block it to prevent any further signals from the uphole geophone or from the Ablaster circuit from being conducted to the recording instrument. The period of time required for condenser |01 to reach its full charge is controlled in such a manner that an impulse delivered to the uphole geophone by vertically traveling seismic waves can be amplified and transmitted tothe recorder before amplifier tube Y used to record signals generated by one of the geophones in the conventional spread. All three signals will be recorded on a single trace withi out any one interfering with the other.

'Ihe microphone 14 and telephone receiver 15 are connected in' this circuit in the same manner as described in connection with the circuit diagram of Figure 4.

A further modification of this invention is shown in detail by the circuit diagram of Figure 6.

By means of this circuit the signal indicative of the instant of detonation of the explosive charge which produces seismic waves, the first' impulse generated by the uphole geophone, andv signals generatedby a geophone of the conventional spread can be recorded on a single trace without one .interfering with either of the others. This circuit like the others described above does not have a polarity discrimination characteristic, that is, the iirst impulse received from the blaster circuit or from the uphole vgeophone whether positive or negative will be transmitted to the recording apparatus and recorded on a trace of the seismogram as truev indications of the exact instants at which they occur.

A signal from the detonating circuit of the blaster is impressed across the primary winding |00 of the transformer ||0. The resultant voltage'in the secondary winding of this transformer is connected through condensers i6 vand 45 to the grid circuits of gas triodes I6 and I1. This voltage will cause an IR drop to be built up across the resistances 41 and 48 due to current flowing through them. One of these IR drops depending upon the polarity of the impulse received from the detonating circuit of the blaster will be positive relative to the negative grid potential existing on the tubes I6 or l1. This positive potential causes the grid potential on one of the tubes to become less negative permitting the tube to re causing a ow of current in its plate circuit to charge condenser 6|. The iiow of the current in the plate circuit o f this gas triode will be in the form of a pulse for when the condenser 6| becomes charged no further plate current can ow and as a result subsequent signals from the blasting circuit will not re the other gas triode. The pulse of current flowing to charge condenser 6| is transmittedl by means of conductor ||2 to the double pole double throw switch I I3, through the switch when it is thrown in an up position, and the conductor H4, through resistor |31, meter |38, resistor |38' to ground and plus 75 volts, through D. C. supply to zero volts and back to the cathode of gastriodes I and |1. This pulse of current causes an IR.A drop across resistor |31, meter |38 and resistor |38. This IR drop is also in the grid-cathode circuit of a repeater tube or translating device ||5 and it is repeated and amplified by tube I5 and transmitted by means of its plate circuit I I6 through lthe contact I1 and one of the arms |06 of the switch I I8 to the primary I9 of transformer |20. 'I'he return circuit is by way of'one of the switch arms |46, the source of anode supply plus 200 volts D. C., and from plus 75 volts D. C. by conductor |45 through the cathode resistor to the cathode of tube ||5. The voltage induced in the secondary winding I2| of this transformer is impressed on the tele'- phone channel that is formed by the conductors 12 and 13. The signal is thus transmitted to the recording galvanometer where it is recorded on one of the traces of the seismogram as a true indication of the exact instant at which detonation of the explosive charge occurred..

After the explosive charge has been detonated 60 of resistanceA |38', by conductor |39 from the seismic waves will travel verticallyfrom the point where the explosion occurred to the surface of the earth where they are detected by a geophone |23 that has beenlocated adjacent the mouth of the shot hole. Sice only the first impulse detected by the geophone is used by the interpreter of the seismogramzno more ofi the signals generated by the geophone are transmitted to the recorder and recorded. Therefore, means re provided as shown in the circuit diagram of-Flgure 6 for suppressing or completely eliminating all signals from the uphole geophone after the rst impulse has been communicated to thev recording instrument.

The'rst impulse .detectedlby the geophone |23,

is communicatea'rb'y -means of the 'transformer 5 former |29, condensers |30 and I3| and theresistances |32 and |33. This signal impulse will in the mannerv described in connection with gas triodes I6 and |1 cause one of the tubes |21 or |28 to fire and'produce a flow of current through resistances |34 or |35 and plate circuit |36 which.

is common to both of the gas triodes. This plate circuit includes the conductor |36, the resistor |31, the milliammeter |38, resistor |38' to ground and plus '15 volts, through plate supply to zero 15 volts and to cathodes of gas triodes of tubes |21 and |28. The iiow of plate current in this plate circuit through resistance |.31 will produce a voltage drop which serves as a bias potential for the grid of amplifier tube H5. At the instant the plate current begins to iiow the impulse of the current building up in this circuit is transmitted through the amplifier tube, conductor IIB and contact ||1 of'switch H8, transformer |20 and the telephone linev formed by conductors 12 and 13 to the recording galvanometer where it is recordedon a trace of the seismogram. Since the plate. current iiowing through the resistor |31 builds up to its maximum immediately; the IR drop across this resistance will bias the amplifier Atube ||5jto cut-off thereby blocking any further signals which would tend to pass through the amplier tube. This in effect isolates the recording instrument from the blaster, uphole geophone, and microphone circuits so that they will not produce disturbances on the trace on which the uphole impulse and time breakimpulse have been recorded that would tend to obscure subsequent signals that are being recorded from a geophone in the conventional spread. Because of 40 the characteristics of gas triodes, plate current will continue to flow through resistance |31 and milliammeter |38 until the circuit has been broken. This can be accomplished by operating switch |51. This operation opens contact |58 which breaks the plate circuit for the gas triodes |21 and |28 and also closes contact |58 and thus discharges condenser 6| through resistance |59'. Switch |51 can be of the push button type in l which the contacts |58 and |59 are resiliently, biased to the position shown in the drawings.

When the contact arms |46 of gang switch ||8 are in the position shown in the drawings, voice communication can be carried on between the recording linstrument operator and the shot flrer by means of the' telephone receiver |41 and the microphone |43. The voice signals are applied to the tube ||5 through a` circuit which may be traced from one side of the battery |42, through the microphone |43, by conductor |44 to one side other side thereof, contact |40, one of the arms v l'|'4|i of switch ||8, and by conductor 4| to the other side of the battery |42. However, when the vcontacts |46 of gang switch ||8 are thrown to their uppermost position the microphone |43 isA ccut out of the circuit and an amplifier with a loud speaker is thrown into the circuit in such a manner that the recording instrument operator can call the shot iirer. This amplifier is a con-n ventional amplifier comprising amplifier tube |49, transformer |50, amplifier tube |5I, transformer |52, and the loud speaker |53. When the contacts |46 of the switch ||8 are thrown to the up position the filament power supplied to the time break circuit, the uphole geophone circuitand the ampliiier tube is cut o. Only the ccnventlonal amplifier and the speaker are then energized. Voice signals transmitted through the telephone channel or lines 12 and 13 appear across the winding IIS of transformer |20, and are applied to the input circuit of amplier tube |49. This circuit may be traced from one side of transformer winding ||9 by the upper arm |46 of switch ||6 and -by conductor |46a to the control grid of tube |49. The return circuit from the 4cathode includes a bias resistance and one oli the switch arms |46 which leads to the other side of .vinding ||9.

The device is shown as operating in conjunction with a vibrator` power pack The low voltpositive side of the terminals |56 is directly connected to the other of the leads |54 leading to the power pack. A pilot light |55 indicates when the power pack is energized. The low voltage. power supply is also applied to the laments of the tubes through a circuit which includes the switch arm |48 of switch IIB. The high voltage from the power pack supplies the entire platev and bias voltages, the voltage being taken from appropriate taps of a voltage divider 250. f

When the uphole geophone is not used the uphole geophone circuit can be disconnected from the remainder of the circuit by throwing the double pole double throw switch ||3 to its down position. 'I'his operation disconnects the laments from all of the tubes inthe uphole geophone circuit and eliminates condenser 6| from the plate circuit of gas triodes I6 and I1. This allows the time break gas triodes I6 and |1 to bias the repeating tube ||5 to cut off. This feature is provided so that the shot rer will have to reset the gas triodes |6 and l1 in order to talk to the recording operator.

Another embodiment of this invention is shown by the circuit diagram in Figure embodiment dilers from those described above in that the time break is transmitted by radio rather than by telephone lines to the, recording instrument without polarity e discrimination. The signal from the detonating circuit of blaster |0 is connected inthe manner described above to the grid circuits of gas triodes |6 and |1 and in the same manner causes one of the tubes to re. and charge condenser 6|. denser 6| is being charged current will flow through resistance |6| in returning to the cathodes of either tube I6 or |1 and will produce an Y IR, drop in this resistance.

Any portion of this IR drop can be taken off of the resistance |6| by means of the contactor |62 and vimpressed on the grid of preamplii'ler tube |63. The output of this amplifier tube is connected by means of the transformer |64 to the modulator of a conventional radio transmitter, the circuit of which is not shown. The amplitude of thev input signal from the time break gas triode circuit to the preasados;

instance it is preferable to use a microphone of the type whose voltage potential |61 is normally disconnected from it. For/this purpose a spring biased switch |66 is provided-which will cause the voltage circuit to the microphone to remain open except when manually held closed.

Battery |69 provides the plate potential for the preamplifier tube |63 as well as the plate potentialfor the gas triodes I6 and |1. When it is desired to reset the circuit it is necessary that the switch |10 be momentarily closed so that the condenser will discharge through the resistor |1|.

During the time the conamplifier tube |63 can be adjusted by means of Switch 9| is provided so that the negative potential can be removed from the grids of tubes |6 and I1 and causes plate current to ow for test purposes. The resistance |12 is placed in series with battery 60 to prevent shorting the battery when the switch 5| is closed.

In Figure 8 there is shown still another embodiment of this invention which is a modification ot the circuits shown in Figures 'l and 6. This circuit includes the necessary apparatus for disconnecting the uphole geophones after the rst impulse generated by it has been recorded on a trace .of the seismogram. 'I'he transmission of the time break and the uphole geophone impulse ln this instance is by means of radio.

In the manner described in connection with Figures 6 and 47 the impulse generated in the detonating circuit of the blaster I6 is communicated to the grid circuits of the gas triodes |6 and |1 to initiate the flow of plate current from one of these triodes |6 or |1, dependent upon the polarity of the impulse received in the grid circuit. In a similar manner the plate current will flow from one of these triodes to charge the condenser 6|. The remainder of the plate circuit is the conductor |13, mllliammeter |14, the battery 62, potentiometer 63, and the conductor |14a, which leads to` the cathodes of the gas triodes I6 and I1. The flow of current through variablel resistance 6 3 while condenser 6| is being charged produces an IR drop which when algebraically added to the potential of the grid bias battery 66 will cause the negative potential on grid |15 of gas triode |16 to become suiilcientlyfless negative that tube |16 will re. The current from the plate of this tube will build up slowly in the plate circuit due to the'inductance 65 and the resistances 66 and 61. This period of time is made yvariable by making the resistance 61 a potentiometer. By moving the-contactor 66 of the potentiometer 61 a period of time amply long for the uphole geophone 16 to transmit to the recording galvanometer the rst impulse detected by it is effected before the pre-amplifier tube |63 has been rendered inoperative to transmit signals. The IR -cutofl and thereby block it so that signals other than the first impulse from the uphole geophone and time break signals cannot be communicated to the recording instrument. Thepreampllilei `'tube |63 is connected in the manner described in Figure '7 through a transformer |64 to a modu-l lator circuit of a conventional radio transmitter, as by conductors 12 and 13. The microphone by means of which the shot nrer can communicate with the operator of the recording instrument is also connected in the circuitin a similar manner to that described and shown in Figure '1.

Still another embodiment of this invention is disclosed in Figure 9. The arrangement of the vconnected in series.

gas triodes I6 and |1 relative to the blaster cirbias potential on grid of gas triodetube |16 to become sufliciently less negative that tube 4|16 will re"to produce a flow of plate current. Resistance |8| is provided in the Igrid circuit of tubes I6 and I1 to prevent shorting battery |80 when switch |82 is closed for test purposes. Resistance |83 isa conventional coupling resistance. The plate circuit of gas triode |16 is divided into three branches comprising in one branch the coupling resistance |83, in a second branch a condenser |84 and variable resistance |85 connected in series and in thevthird branch a variable resistance |86, condenser |81 and resistance |88 At the instant the gas triode |16 res and plate current begins to ow, since condenser |81 and resistances |86 and |88 have .f

a small time constant, condenser |81 will become charged quickly, after which current will -no longer iiow in the third branch of the plate circuit. This impulse of current which charges condenser |81 produces an IR dropacross the Figure 10, complete control of the period of time during which signals from the uphole geophone are being recorded is possible. In this cir-cuit, the time break is transmitted exactly the same y as in rFigure 6. 'I'he signal from the uphole geophone |23 is amplified and repeated through the two stage amplifier consisting of transformer 26|, repeating tube 262, transformer 263, repeating tube 264', transformer 265 to the telephone lines 12 and 13. The rst impulse from the uphole geophone |23 after having been amplied by the tube 262 will be transmitted to the grid of gas triode 266 by means of conductor 261 and condenser 268. This impulse will drive the grid of tube 266 less negative and cause the plate of tube 266 to conduct. This current iiows through re- 1 sistance 269, contact 210 of switch 21|, resistance resistance |86 and a portion of this IR drop ls 1 tapped off and conducted by conductor |89 through an uphole geophone |98 to the grid circuit of a preamplifier tube |63. The signal from tlie plate circuit of tube |63 is communicated to the modulator circuit of a conventional radio transmitter through the medium of transformer |64, and transmitted to the recording instrument by radio where it is received and recorded on a trace of the seismogram. After condenser |81 in the third branch of the plate circuit of tube |16 has become charged and current ceases to iiow in this branch, condenser |84 will be charged. The capacity of this condenser is selected such that the time required for it to become fully charged will be sufciently long to permit the uphole geophone |96 to detect and transmit through the preamplifier tube |63 the first impulse received by it. As soon as the condenser |84 is fully charged,

the charging potential as derived from resistance |83 is effective in biasing the preampliiier tube |63 beyond plate current cutoff. By blocking tube |63, no further signals, whether from the microphone 66 or from the uphole geophone |90, can produce modulation. This permits the trace on the sesmogram on which the time break'impulse and the uphole geophone impulse have been recorded to be used to record signals detected by one of the geophones in the conventional spread without interference. The microphone |66 and transformer |61 are connected in such a manner that the shot rer can speak to-the operator of the recording instrument.- A

lAnother modication of Figure 6 is shown in Figure 10. In using electrical circuits of the type described' above, it is often desirable to have an arrangement whereby the true character of the signal detected by the uphole geophone can be recorded or at least as much of the signals lfrom this geophone as are desired. Additionally, it is often desirable to be able to evaluate signals such as casing breaks which travel at substa'ntially the same velocity as the waves that travel vertically upward to the uphole geophone.

v By means of the electrical circuit `illustrated in drop is of such value and polarity that it will in- '212, conductor 213, to plus 75 volts D. C., to 0 volts D. C., conductor 214, resistor 215, and back to cathode of gas triode 266. This current produces an IR drop across resistance 215 which charges condenser 216 through resistance 211. The polarity of the voltage of condenser 216 is such that it reduces the negative grid voltage of gas tube 218 as supplied by the voltage divider. When the potential of condenser 216 reaches a certain valuethe grid of tube 218 will lose control and ythe plate circuit of tube 218 `conducts current through switch 219, contact 288 of switch 21|, resistor 28|, meter 282, resistance 283, resistance 284, to Iground which is plus '75 volts D. C., tol plus 5 Volts D. C. and to the cathode of tube 218. The time required for condenser 216 to become charged to the critical value for tube 218 is determined by the capacitance of condenser 216 and value of resistance 211. Since the time of arrival of the first energy is the desired information, the time constant is set so that tube 218 will trip or start conducting on theorder of .01 to .02 second after the first impulse has tripped gas triode 266. When the plate current of tube 218 iiows through resistances 283 and 284 andmeter 282 an IR drop exists across them. 'Ihis IR lowing signals from the uphole geophone |23 out. Additionally, it will prevent the shot firer from speaking to. the recording operator over the.

microphone circuit composed of microphone 285, battery 286, and resistor 284. This arrangement requires the shot iirer'to'ieset the apparatus by closing push button switch-21| down.

When" the uphole time is not desired, switch 219 is turned to oi" position. `This cuts'oi the plate of tube 218 and shorts out condenser 6|.

' With these changes made, the time break pushpush gas triodes I6 and I1 conduct upon the arrival of an impulse from the blaster and this current flbws through meter 282, and resistances 284 and 283 which produces an IR drop that disables repeating tube 264. As inthe previous instance reset switch 21| must be thrown in the down position to cut the current out of the meter 282 and resistors 284 and 283.

Under some conditions the gas triode tube is subject to ring upon the sudden application of eliminated from the trace.

in the diagram The switch is opened by means of a push button and upon releasing the push button the switch returns immediately to the position shown. Assuming that the plate of tube 218 is conducting, switch 21| is then opened. Current continues to the plate byway of condenser 281 until the' condenser becomes charged. This charge is approximately equal to the plate voltage available for the plate of tube 218. When switch 21| is released, condenser 281 discharges through resistor 28| and produces an IR drop which is opposite to the plate voltage. At first it is seen that the voltage reaching the plate of the tube 218 is very low. As the condenser 281 becomes discharged and its resulting dischargev current IR drop in resistance 28| decreases, the voltage on the plate comes up to normal. The same results are obtained in the plate current of tube 266 by means of condenser 288, contact 210 of switchY 21|, and resistor 212.

Figure 11 illustrates a typical record showing only two traces. 'Irace a has recorded thereon a time break impulse and the ilrst breaks occasioned by signals which have been generatedby a geophone in the conventional spread. Trace b shows only Va record of the signals which have been generated by an uphole geophone which has been placed adjacent the shot hole. On trace a there is shown a succession of secondary breaks which follow the time break impulse. These secondary breaks are due tosignals developed in the detonating circuit after the detonation of the explosive charge and are Vcaused by making and breaking the detonating circuit by the ends of the conductors to which the electric blasting cap was connected coming in contact with each other or the casing of the shot hole. Additionally, it will be noted that there is recorded on trace a at c, a high frequency wave of low amplitude. The sig-v nals which produced this wave also originate in the blasting circuit and are caused by commutator ripple in the blaster itself.` In order tor record the time break, the uphole geophone impulse and the first break from a geophone in the conventional spread on the same trace, it is necessary that the spurious .voltages corresponding to the secondary breaks and the commutator ripple be eliminated from the record. By comparing traces a and b it will be seen' that if an attempt is made to record the uphole geophone break on a record which has secondary breaks and commutator ripple recorded thereon, the uphole break would be indistinguishable.

By using the invention forming the subject matter of this application, a record such as that illustrated in Figure 12 can be recorded. On

trace d, there is shown a definite time break and The spurious voltages which cause secondary breaks and commutator ripple have been entirely By comparing trace d with trace e, it is obvious that the record of the uphole -geophone impulse .could be recorded on the same trace with the time b reak and the rst break occasioned by a geophone in the conventional spread.

In Figure 13` there is illustrated a trace of a seismogram on which the time break impulse, the uphole geophone break and the first break from a geophone in the spread are all distinctly recorded on the same trace. It will be noted that each signal is definite and can be accurately read vby the interpreter.

The trace shown in Figure la diiers from that to reflected waves are also recorded on the same trace with the other three data. This trace represents an ideal record for it has all of the data recorded on it that is needed from a particular spread when shot in one direction. It will be noted that after the rst break has been recorded from the geophone in a spread, that the gain in amplification is suppressed .to some predetermined minimum value and automatically expanded with time in such a manner that all of the signals corresponding to reflected waves are recorded with substantially the same amplitude.

Although this invention has been described in detail in connection with the use of hot-cathode control-grid type tubes commonly known on the market as types 884 and 885, it is obvious to those skilled in the art that these triodes can be replaced by cold-cathode starter-anode type gas triodes. These are generally known on the market as 0A4-G gas triodes. A shield is indicated in the gas tubes of Figure 6 and Figure 10. These are referred to as gas triodes. 'I'hey are in fact gas tetrodes, due to the additional element.

These are of the RCA 2051 type. The general characteristics of the gas triode and gas tetrode are the same.

We claim: l

1. In a system for recording a time break impulse, an uphole geophone impulse and all oi the signals generated by the detector in a conventional spread on a single trace of a seismogram having means for generating coincidentally7 with the instant of detonation of an explosive charge a transient volta-ge which may include a plurality of impulses of opposite polarities, means for communicating said transient voltage to a point removed from the point of detonation of the explosive charge, means at said point for receiving said transient voltage and responsive to the ilrst impulse thereof regardless of its polarity for generating a voltage impulse, means for recording this said voltage impulse on a trace of a seismogram as an indication of the instant of detonation of the explosive charge, means interposed between said transient voltage receiving means and said recording means for thereafter blocking signals generated in the detonating circuit, means for applying to said recording means a signal representative oi said uphole impulse, and means operable by the said detector for applying signals detected thereby to said recording means.

2. In a system for recording a time break impulse that is indicative of the instant of detonation of an explosive charge to create seismic waves in the earths surface having means for generating a voltage impulse coincidentally with the instant of detonation of the explosive charge, means for transmitting said voltage impulse to a point removed from the point of detonation c f the explosive charge, the combination of means at said point actuated by the voltage impulse regardless of its polarity, for generating a second voltage impulse, means for recording the second voltage impulse as the. time Vbreak impulse on a trace of a seismogram, and means interposed between said second voltage impulse generating means and the recording means for blocking all signals generated subsequent to the impulse that is indicative of the .instant of detonation, whereby other data can subsequently be distinctly re corded on the same trace.

3. An apparatus for producing and .transmitting a signal indicative of the instant of detonation of an explosive charge to create seismic waves in the earth that comprises in combination, means for generating a voltage impulse coincident with the detonation of the explosive charge, a pair of gas triode tubes, a common plate circuit for said pair of gas triode tubes, a condenser in said plate circuit, means for placing a common negative bias potential on the grids of said tubes, means to conduct the initial voltage impulse to the grids of said tubes whereby the grid potential of one oi the pair of tubes will become less negative to permit current to flow through the plate circuit in that one tube and to thereby rapidly charge the condenser in the plate circuit to prevent vfurther ow of current in said common plate circuit, .and means l operable by the iow or" current in said common plate circuit for said tubes to produce a voltage impulse coincident with the instant of detonation of the explosive charge, and means recording this voltage impulse on a seismogram as a true indication of the time ci detonation or" the explosive charge.

4. An apparatus for producing and transmit-l ting a signal indicative oi the instant of detonation ci an explosive charge to create seismic waves the earth that comprises in combination, means for generating a voltage impulse coincident with the detonation of the explosive charge, a pair of gas triode tubes, a common plate circuit for said pair of gas triode tubes,

said plate circuit consisting lof at least one re-.

sistance element and a condenser, means for placing a commonnegative bias potential on the grids of said tubes, means to conduct the initial voltage impulse to the grids or said tubes whereby the grid potential of one of the pair of tubes will become less negative to permit current` to flow ythrough the plate circuit in that one tube and to thereby rapidly charge the'condenser in the plate circuit to prevent further flow of current in the said common plate circuit, and means operable instantaneously upon the iiow of current across said resistance in the plate circuit to transmit a voltage impulse coincident with the instant ofv detonation of the explosive charge, and means for recording this voltage on a seismogram as a true indication of 4the time of detonation of the explosive charge. x

5. An apparatus for producing and transmitting a signal indicative of, the instant of detonation of an explosive charge to create seismic waves in theearth that comprises in combination, means for generating a voltage impulse coincident with the detonation of the explosive charge, a pair of gas triode tubes, a plate circuit for each tube, a condenser and a resistor in series and common to the two plate circuits, means for placing a common negative bias potential on the grids of said tubes, means to conduct the initial voltage impulse to the-grids of said tubes whereby the grid potential of one .of the pair of tubes will become less negative to permit current to ow through the plate circuit in that one tube and to thereby rapidly charge the condenser common to the two plate circuits and thereafter to prevent further ow of current in said plate circuits; means for transmitting the voltage impulse produced by the current ow through said resistor, and means for recording this voltage, impulse on a seismogram as a true indication of the time of detonation of the explosive charge.

6. An apparatus for producing and'transmitting a signal indicative of the instant of detolll nation of an explosive charge to create seismic waves in the earth that comprises in combination means for generating a voltage impulse coincident with the detonation of the explosive charge, a pair of gas triode tubes, a plate 'circuit for each tube, a condenser, a resistor and a current source in series and common to the two plate circuits, means for placing a common negative bias potential on the grids of said tubes, means to conduct the initial voltage impulse to the grids oi said tubes whereby the grid potential of one of the pair of tubes will become less negative to permit current to flow through the plate circuit in that one tube and to thereby rapidly charge the condenser common to the two plate circuits and to prevent further now of current ,in said plate circuits, means operable upon the flow of current through 4said resistor to 'transmit a voltage impulse coincident with the instant of detonation of the explosive charge, and means for recording this voltage impulse upon a seismogram as an indication of the time of detonation of the explosive charge, whereby regardless of the polarity or said rst mentioned voltage impulse current will now through said resistor and the record made by the last mentioned voltage impulse will be a true indication of the instant ordetonation or the explosive charge.

if.. in a system for producing and transmitting a signal indicative of the instant of crea-- tion of seismic waves in the earth, the combination o a pair of tubes each having a grid, an

anode, and a cathode, and the characteristic oi iiowv of anode current regardless of grid bias once the grid loses control, an input circuit for said tubes which includes means negatively biasing each grid normally to prevent ow of anode current, means operable coincidentally with the creation of said seismic waves for applying a voltage impulse to said input circuit in manner such that the polarity of said impulse reduces the negative bias upon one grid to initiate current flow through that one tube, an output circuit which includes the anodes of said tubes l and means operable immediately upon said current ow in said output circuit for thereafter preventing further current flow in said output circuit, and means operable by the initial curlrent ow in said output circuit for producing acteristic of continued flow of anode current once said control electrode loses control, means for negatively biasing each control electrode to preventfcurrent fiow within its tube, means for.

applying said voltage impulse to said control electrodes so that an impulse of one polarity increases the negative bias on one electrode while simultaneously decreasing the negative bias on the other control electrode, a common output circuit for said tubes including a series condenser and a source of anode operating potential, the decrease in negative bias on said one of said tubes producing current ilow therein until said series condenseris charged, and means operable by the flow of current in said output circuit for producing a voltage impulse coincidentally with the instant of creation of said seismic waves, said series condenser thereafter preventing current ow through either of said tubes regardless of the magnitude and polarity of subsequently applied `voltage impulses to the control electrodes thereof, and means for recording on a seismogram as a true indication of the time of creation of,said seismic waves the voltage impulse produced as a result of current flow in said output circuit.

9. In a system for producing and transmitting a signal indicative of therinstant of creation of seismic Waves in the earth, the combination of a pair of tubes each having a, grid, an anode, and a cathode and the characteristic of ilow of anode current regardless of grid bias once the grid loses control, an input circuit for ascaosi said tubes which includes means negatively biasing each grid normally to prevent now of anode current, means operable coincidentally with the creation of said seismic waves for applying a voltage impulse of one polarity to said input circuit, said impulse of said one polarity increasing the negative bias upon the grid of one tube and reducing the negative bias upon the grid of the other tube to initiate current flow therethrough, an output circuit which includes the anodes of said tubes. means operable-im mediately upon said current ow from said one tube to prevent current flow through the other f: of said tubes, means operable by the ilow of plate current from said one tube to producel a voltage impulse coincidentally with the instant of creation of said seismic waves, and meansY 20 ation of said seismic waves.

EARLEY M. SHOOK. ROBERT W. OLSON, 

